Corrective lenses may be provided in many forms for correcting a variety of vision deficiencies and impairments and to suit various needs and applications. Rigid corrective lenses constructed from glass or plastics are traditionally mounted in eyeglass frames worn by an individual. Various types of contact lenses have been developed in recent years that provide a rigid or flexible corrective lens that contacts the eye of the wearer directly. Eyeglasses and contact lenses provide satisfactory optical correction and convenience under many circumstances.
Many individuals require more than one type of optical correction. As individuals age, for example, they frequently require optical correction, i.e. magnification, for reading applications, as well as optical correction for seeing well at distances. An individual requiring multiple optical corrections may use two or more pair of eyeglasses, each providing a different optical correction for a particular application. This approach is inconvenient, requiring an individual to carry two or more pair of eyeglasses and change eyeglasses, depending upon whether the individual is reading, looking at a distance, etc. In many circumstances, an individual needs to see at a distance and read intermittently, so that maintaining, transporting and changing two or more pairs of eyeglasses is impractical.
Eyeglasses having bifocal and trifocal corrective lenses have been developed in an effort to provide a convenient solution in which a single pair of eyeglasses may be used for distance, intermediate and reading applications. The prescriptive lens for reading is generally placed in the lower region of the lens, while the prescriptive lens for seeing at distances is placed in an upper and/or central region of the lens. Various arrangements of lenses, including placement of a prescriptive lens for reading in an upper region of the lens, have also been provided in bi- or multi-focal lenses for specialized occupational applications. Wearing a single pair of eyeglasses having multiple corrective lenses of this type is more convenient than changing eyeglasses each time a different optical correction is required.
Many individuals, however, have difficulty adjusting to bifocal or trifocal lenses. Lenses providing multiple corrections in different regions do not provide a full field of view for any correction. There may be serious safety issues, for example, when an individual wearing conventional bifocal or trifocal lenses goes up or down stairs or needs to navigate curbs or other uneven terrain. Conventional bifocal and trifocal lenses are also not well suited for recreational or sporting activities such as hiking, skiing, playing various sports, and the like. To participate in these activities, an individual may need to purchase and transport additional eyeglasses. This is both inconvenient and expensive. There thus are many situations in which bifocal or trifocal lenses are not optimal and having multiple pairs of eyeglasses may be desirable or necessary.
The eyeglass situation is further complicated by the desirability of having lenses that are protective, such as those provided in sunglasses, particularly for sporting and outdoor recreational activities. Many individuals elect to purchase prescription sunglasses having a single type of corrective lens to correct, for example, distance vision. These eyeglasses are suitable for sporting and recreational activities, but cannot be used for other activities requiring a different correction, such as reading.
Detachable clip-on lenses have been developed to "convert" eyeglasses having single or multiple corrective lenses to sunglasses. Generally speaking, clip-on lens assemblies having tinted or polarized or UV-protective lenses are a convenient and cost-efficient approach to satisfying multiple optical requirements. The detachable lens assembly may employ a mechanical clip, magnets, or other means to permit removable mounting to conventional eyeglasses. Clip-on radiation shielding lenses that "convert" prescription eyeglasses to radiation protective prescription eyeglasses have also been used.
Specialized magnifying lenses have been designed for use in professions such as surgery, jewelry making and repair, and the like. Such specialized lenses are mounted in a housing that may be mounted to a pair of base eyeglasses on a bar extending from the eyeglass frames. Such specialized lenses may be flipped up or pivoted out of the way at times when the specialized correction is not required. This system is cumbersome and inconvenient.
U.S. Pat. No. 3,033,359 discloses a disposable lens shield constructed from an electrostatic-type of transparent plastic which adheres readily to an eyeglass lens when placed in contact with the lens. The lens shield may be tinted with a dye to reduce transmission of harmful light rays and, thus, prescription-ground eyeglasses may be converted quickly, easily and economically into prescription-ground sunglasses. The disposable lens shield may also be used to protect the eyes of industrial workers from foreign particles and to protect glasses or goggles from materials such as paint.
PCT International Application PCT/US94/14271 discloses aliphatic thermoplastic polyurethane "press-on" lenses that are permanently but releasably adhered to base eyeglasses. The lenses are optically clear and can be adhered to sunglasses or other plano (non-prescriptive) lenses using molecular surface adhesion to mount magnifying or corrective lenses to eyeglasses. The lenses are removable from the base eyeglasses only with considerable effort. The press-on lenses are generally applied to the inner surface of the rigid lens of eyeglasses or sunglasses to provide a correction, such as a magnification. Thus, eyeglasses may be "converted" to bifocals or trifocals by applying one or more detachable thermoplastic polyurethane lenses. A plurality of magnifying or corrective polyurethane lenses may be mounted on the surface of a base lens. In one embodiment, detachable thermoplastic polyurethane lenses are applied to both the inner and outer surface of a lens in an orientation such that the applied lenses are twisted or rotated in relation to one another to provide correction for an astigmatism. Placement of the detachable lenses are illustrated in conventional arrangements, with magnifying corrective lenses applied on the lower and lower-central area of the base lens.
U.S. Pat. No. 5,464,094 similarly discloses stick-on lenses designed to adhere to the interior surface of the lenses of a pair of sunglasses or non-corrective eyeglasses. Packaging containers for displaying the stick-on lenses are also disclosed.
Many occupations require individuals to read information presented on a vertically oriented panel or display, or at a level even with or higher than eye level. Radiologists, anesthesiologists, surgeons, and many types of medical technologists, for example, need to read films, computer screen image and data displays, various instruments, and the like that are displayed vertically. Similarly, airline pilots, mechanics, plumbers and many medical personnel are required to read information or instruments or see work displayed at a level even with or higher than eye level. Also, computer workstations are generally arranged so that a generally vertically oriented computer monitor is placed even with eye level or slightly lower than eye level.
Use of conventional bifocal corrective lenses in situations where the displayed or reading material is presented on a generally vertical display or is even with, higher than or even slightly lower than the individual's eye level requires the individual to tilt his or her head and neck in an uncomfortable position to view the displayed or reading material through a conventional bifocal corrective magnifying lens placed in the lower region of the lens. Repetitive and serious neck strain and back problems are common among health care workers, computer users, and other individuals whose occupations require such unnatural positioning of the head and neck.
Another problem that is particularly acute in occupational settings is that conventional corrective lenses, such as bifocals, are typically designed for reading at a particular distance, i.e. 18 inches, which may not be a suitable distance in an occupational setting. Computer monitors and other types of vertical displays, for example, are frequently arranged a greater distance from the user's eyes, and the conventional corrective lenses provided for reading frequently are not suited for viewing such displays. The individual tends to lean forward under these circumstances, aggravating neck and back problems. It would be useful, therefore, to provide an intermediate strength corrective lens that can be used for such applications but that is not otherwise useful in daily wear eyeglasses.